The invention relates to systems and methods for guiding and locating diagnostic or therapeutic elements on medical instruments positioned in a body.
The use of invasive medical devices, such as catheters and laparoscopes in order to gain access into interior regions or spaces of the body for performing diagnostic and therapeutic procedures is well known. In such procedures, it is important for a physician or technician to be able to precisely position the device, including various functional elements located on the device, within the body in order to make contact with a desired body tissue location.
For example, the need for precise control over the positioning of an invasive catheter or surgical probe is especially critical during procedures for testing or ablating myocardial tissue within the beating heart for treating cardiac rhythm disturbances. To perform such a procedure, the physician typically steers a catheter through a main vein or artery into the interior region of the heart that is to be treated. The physician then manipulates the catheter in order to place one or more electrodes carried on the distal portion and/or tip of the catheter into direct contact with the endocardial tissue. The physician may use the electrode(s) to examine the propagation of electrical impulses in heart tissue in order to locate aberrant conductive pathways and to identify the arrhythmia foci. This procedure is called mapping. One such mapping technique is to introduce multiple-electrode array structures carried on the distal end of an invasive catheter into the heart through venous or arterial access. Information obtained from the various electrode elements (operating in either unipolar or bipolar fashion), combined with externally obtained electrocardiogram signals, can be externally processed to detect local electrical events and identify likely arrhythmia foci locations within the heart.
Using the same, or a different catheter or surgical probe device, the physician may then direct energy from one or more distally carried electrode(s) through the myocardial tissue either to an indifferent electrode (in a unipolar electrode arrangement) or to an adjacent electrode (in a bipolar electrode arrangement) to ablate the tissue locations containing the aberrant conductive pathways in order to restore a healthy heart rhythm. This procedure is called ablation therapy.
In theory, minimally invasive mapping techniques allow a physician to identify a target ablation site within the heart, prior to the actual ablation procedure and without the complications of open heart surgery. In practice, however, current minimally invasive mapping techniques do not ensure that an identified target site will be accurately or easily relocated. Accordingly, it would be desirable to provide physicians with the ability to accurately return to a target site in the heart that was previously identified using minimally invasive mapping techniques.
One proposed solution to the problem of identifying and relocating target sites in the heart site is to add a navigation system that is centered outside of a patient""s body, in order to provide an xe2x80x9cabsolutexe2x80x9d reference frame that is unaffected by the absolute location of the patient. One such system, disclosed in U.S. Pat. No. 5,391,199 to Ben-Haim (xe2x80x9cthe ""199 patentxe2x80x9d), combines an electrophysiological mapping system and a navigational system centered on a reference frame outside of the body in order to attempt to increase a physician""s ability to return to an identified target site. The mapping system provides data on points of interest at sites within the body. The exterior navigational system provides data on the xe2x80x9cabsolutexe2x80x9d location of the site with respect to an external reference frame of the site as these points of interest are identified. This is accomplished by placing one or more location sensors adjacent mapping elements on the mapping probe. As taught in the ""199 patent, combining the xe2x80x9clocation informationxe2x80x9d with xe2x80x9clocal informationxe2x80x9d for a sufficient number of sites will provide a three dimensional xe2x80x9cmapxe2x80x9d of data points corresponding to the three-dimensional structure of the heart or other organ.
One problem, however, occurs with mapping catheters having relatively small mapping element carrying structures, e.g., 3-D catheter structures that are 40 mm in diameter or smaller. In these cases, it is difficult to place location elements adjacent all of the mapping elements, and sometimes even adjacent a select few of the mapping elements. Thus, generating a three dimensional map is made difficult. Another problem occurs as a result of the discrete nature of the mapping elements. Oftentimes, critical information is missed between the mapping elements, resulting in a map that, although corresponding to the three-dimensional structure of the heart or other organ, does not accurately identify target sites.
The present invention provides for systems and processes for refining a registered map.
In a first aspect of the present invention, a method of mapping a body cavity of a patient is provided. The body cavity may be, for example, a heart chamber. A first probe carrying a plurality of mapping elements is positioned adjacent a plurality of locations along the body cavity. The first probe may include a 3-D catheter structure on which the plurality of mapping elements is carried. In one embodiment, the 3-D catheter structure is 40 millimeters or less in size. A second probe carrying a functional element is also positioned in the body cavity. The absolute position, within a three-dimensional coordinate system, of the functional element is determined. Also, the proximity of that functional element to each of the plurality of mapping elements is determined. Based on the absolute position of the functional element and the proximity of the functional element to the mapping elements, an absolute position within the coordinate system of the mapping elements is determined. A map is generated by detecting information local to the body cavity, with the mapping elements, and associating the local information to the absolute positions of the mapping elements. The functional element is then located adjacent a location on the body cavity between the plurality of locations. Here, the functional element of the second probe comprises a mapping element. Prior to locating the functional element adjacent the body cavity location, in one alternative, the first probe is removed from the body cavity. In another alternative, the first probe is maintained within the body cavity while locating the functional element adjacent the body cavity location. The absolute position of the mapping element of the second probe, within the coordinate system, is determined. Additionally, information local to the body cavity is detected using the mapping element, and the local information is associated to the absolute position of the mapping element in order to refine the map.
In an alternative procedure of the first aspect of the present invention, a first probe carrying a plurality of mapping elements are located adjacent a plurality of locations along the body cavity. A second probe carrying a mapping element is positioned in the body cavity. An absolute position within a three-dimensional coordinate system is determined for each of the plurality of mapping elements. A map is generated by detecting local information using the plurality of mapping elements and associating that information to the absolute positions of the plurality of mapping elements. The mapping element of the second probe is adjacent a location on the body cavity between the plurality of locations. An absolute position of the mapping element is determined, local information is detected using the mapping element, and the local information is associated to the absolute position of the mapping element in order to refine the map.
For either of the above-mentioned procedures, the refined map is stored in memory, the refined map is retrieved from memory, and the refined map is displayed. A device is navigated within the coordinate system by reference to the displayed refined map. The navigated device may be the second probe. The navigated device may also be a therapeutic device used to treat targeted tissue identified by the local information. The therapeutic device may include an ablation element to ablate the targeted tissue.
In a second aspect of the present invention, a method of mapping a body cavity of a patient is provided. The method comprises positioning a mapping probe within the body cavity, generating a map of the body cavity with the mapping probe, and registering the map within a three-dimensional coordinate system. This can be accomplished using the previous map registration methods, or alternatively, using other map registration means. The method further comprises positioning a roving probe in the body cavity and refining the map with the roving probe.
The preferred method of refining the map may include locating the mapping element adjacent a location on the body cavity, determining an absolute position of the mapping element within the coordinate system, and detecting information local to the body cavity using the mapping element and associating the local information to the absolute position of the mapping element. Alternatively, other means of refining the map can be used. The preferred method may further include storing the refined map in memory, retrieving the refined map from memory, and displaying the refined map. A device can be navigated in the coordinate system by reference to the displayed refined map. The device can be a therapeutic device and the refined map can comprise information indicating tissue targeted for therapy, in which case, the method can further comprise treating the targeted tissue with the device, e.g., by ablating it with an ablation electrode. The mapping probe can be removed from the body cavity prior to refining the map, or alternatively, maintained within the body cavity while the map is refined. The body cavity can be a heart chamber or any other body cavity within the patient.
In a third aspect of the present invention, a system for mapping a body cavity is provided. The system includes a first probe having a distal portion carrying a plurality of mapping elements and one or more location elements, and a second probe having a distal portion carrying a mapping element and a location element. In one embodiment, the first probe includes a 3-D catheter structure to carry the plurality of mapping elements. In an embodiment of this first probe, the 3-D catheter structure is 40 millimeters or less in size. A mapping processing subsystem is provided that is in communication with the plurality of mapping elements and the mapping element. The mapping processing subsystem is configured for generating a map by detecting information local to the body cavity using the plurality of mapping elements and the mapping element. A location determination subsystem in communication with the one or more location elements and the location element determines absolute positions of the plurality of mapping elements and the mapping element in a three-dimensional coordinate system based on locations of the one or more location elements and the location element. A registration subsystem in communication with the mapping processing subsystem and the location determination subsystem associates the local information to the absolute positions of the plurality of mapping elements and the mapping element. Memory in communication with the registration subsystem is used for storing the refined map, and a display is used for displaying the refined map. In an alternative embodiment, a device carrying another location element, wherein the location determination subsystem is further in communication with another location element and is configured to determine an absolute position of the another location element, is provided. This device may be the second probe. Also, this device may be a therapeutic device, and may include an ablation electrode, capable of treating tissue targeted for therapy that is identified by the local information.
Other and further aspects and features of the invention will become apparent from the following drawings and detailed description.